The present invention relates to data transmission in a vehicle navigation system. More specifically, the present invention provides a protocol for transmitting data between a navigation computer and a vehicle controller which controls a variety of vehicle systems including a user interface by which a user interacts with the navigation computer.
There are currently a wide variety of commercially available on-board navigation systems for automobiles the majority of which are substantially self-contained. That is, most of today's systems are largely separate from the vehicle's systems requiring only input from the vehicle's odometer. All other functions of such navigation systems, including those of the user interface, are performed independent of the vehicle's other system. FIG. 1 is a block diagram of a vehicle navigation system 100 designed according to the prior art. A navigation computer 102 receives input from the vehicle's odometer 104, a gyroscope 106, and a global positioning satellite system represented by satellite 108. Navigation computer 102 uses this input along with digitized map data in a database medium 110 to perform navigational functions such as route calculation and guidance. Navigation system 100 interacts with a user via user interface 112 which typically includes a display screen and some sort of keypad for user input. When a user enters a command via interface 112 which requests, for example, that a list of cities be displayed, navigation computer 102 typically loads the entire list from database 110 into its local memory (not shown) and then transmits the list to the display as the user scrolls through it. This is done regardless of the size of the list because the transmission between computer 102 and interface 112 is typically the limiting part of the data transfer path. It is expected by many in the vehicle navigation industry that trends in automobile design will soon render this design paradigm obsolete.
As automobile design progresses, the control mechanisms for the various vehicle systems are becoming increasing sophisticated. Individual microprocessors and controllers currently play an important role in the operation of and the interaction between most electrical and mechanical vehicle systems. It is envisioned that the operation and interaction of substantially all vehicle systems will eventually be controlled by a single central controller. It is also envisioned that a sophisticated user interface having a display and some sort of keypad will be provided by which the user of the vehicle may configure various vehicle systems.
The advent of such a control Environment in automobiles of the future will of course necessitate a change in the nature of vehicle navigation system design. For example, most navigation systems available today have a dedicated user interface with a display and some sort of input device. However, in the vehicle of the future described above, such a user interface would be duplicative of the vehicle's interface. Also, because the vehicle of the future will control most vehicle functions with a central controller, it is likely that at least some input information going to the navigation system will come through the central controller. Thus, some sort of interface with the central controller will probably be necessary.
Moreover, because current navigation systems are largely self-contained, when such systems display a list of cities or streets in the user interface, the entire list is typically retrieved from the map database and stored in local memory even though only a relatively small portion of the list may be shown at any one time. This would obviously not be appropriate for a navigation system which interacts with the user interface through an external controller. That is, the central controller could not allow its memory to be consumed in this way because of the memory demands associated with other systems under the controller's purview. In addition, if the central controller had to wait for a list of all the street names in a large metropolitan area to be downloaded from the navigation system before displaying the list, the delay would be unacceptable from a marketability perspective.
Finally, given the complexity of the control environment of the vehicle of the future, it simply makes sense to bring the operation of the navigation system at least partially under the control of the vehicle's central controller.
It is therefore desirable to provide a vehicle navigation system which is operable to interact with the vehicle's user interface and other systems via the vehicle's central controller.